Chaos Theory
by gummybookwerm
Summary: When Bonnie's magic is out of control, who will she turn to for help? The answer is obvious, but the outcome? Not so much...
1. Chapter 1

"If he was a book, you'd have barely made it past the _Acknowledgements_."

"Please," Bonnie scoffed. "You think I don't know that?"

"And yet you still agreed to help him."

"Yes, _help him_ , Damon. That doesn't mean I trust him."

"How can you be so sure he isn't just trying to trick you?"

"Trick me into doing what, exactly?"

"I don't know! Something evil."

"So you're saying I'm stupid enough to be tricked into doing 'something evil' without knowing it."

"No!"

"Damon, he _shot me_ with an _arrow_ ," she spoke slowly, over-enunciating every word. "He strangled me, stabbed me, stole my magic and left me for dead."

"Yeah well that hasn't stopped you in the past."

"What are you talking about?"

"Think back to that oh so lovely time I tried to _literally_ bite your head off," Damon's blue eyes flashed beneath his dark brows, the memory of sinking his teeth into her throat now apparently an unpleasant one to recall with their updated friend-status. "Now look at us – besties."

"You're right Damon; I've actually grown bored of you and am looking to fill the vacancy in my social circle with someone even more annoying."

Damon, for once, seemed to be at a loss for words. His jaw worked soundlessly as he raked frustrated fingers through the already tangled mop atop his head. She pushed forward; taking advantage of the quiet as he struggled to recover from her sarcastic dismissal.

"Damon, _listen to me_ ," she bit out, uncrossing her arms and leaning forward to press her palms against the cool countertop between them. "I _know_ he's a liar and a manipulator. I _know_ he's dangerous– "

"Do you? Because any rational person with two brain cells to rub together would take one look at the SparkNotes of this situation and be able to figure out it's a stupid idea and someone is going to end up dead. Hell, we've already got a stellar example! I wonder what witchy-twin number two would be up to today if he wasn't _six feet under_."

"That's why I have to–"

"There's no 'I' in team, Bon."

Her nostrils flared in response to his mocking tone, "This isn't –"

"This isn't your responsibility is also _not_ a valid point because _he_ ," he hissed, aiming an accusatory finger outside, as though the 'he' in question was lounging in the yard, "Isn't your responsibility either!"

 _"I let him out!"_

Her snarl was answered by a loud yelp, followed by a string of profanity as Damon shot away from the windows above the kitchen sink, his blistered skin sizzling unpleasantly.

A jolt of anxiety squeezed Bonnie's chest, causing her heart to thud against her ribcage as she tried to get a handle on her irritation. Gritting her teeth against the magic simmering under her skin, she forced herself to take deep calming breaths until it reluctantly retreated, churning with a palpable displeasure.

"What the hell, Bonnie?! This is my favourite shirt!"

She turned, holding back a snort when she caught the look of the utter dismay on her friend's face as he poked a finger through one of the smoking holes in his newly distressed T-shirt.

" _Was_ , and I'm not asking for your permission Damon," she snatched her jacket off the bar stool it was draped over, marching past him and making it as far as the front hall before a hand clamped down on her shoulder, spinning her around to face his frosty scowl.

"You aren't stepping foot outside this house until I figure out a way to kill that little psychopath and make it stick."

"Along with the rest of the Gemini coven?"

"If that's what it takes."

Her jaw nearly hit the floor.

Wrenching herself from his grip, she shoved her arms violently into her jacket, huffing as she freed her hair from the collar and made a b-line for the door. He was such a hypocrite. She managed to get the door open a crack before his arm shot over her shoulder to slam it shut, her annoyance spiking when she noticed his skin had returned to its usual immaculate alabaster condition.

Stupid vampires.

"Damon!"

"Bonnie."

She could practically hear his smirk. Her skin felt like it was burning hot and cold at the same time, magic coiling eagerly in her belly, ready to burst out if she lost control for even a second –

 _"Move."_

"Oh I'm sorry, which part of _'you aren't stepping foot outside this house'_ did you not understand?"

Whirling around, she shoved ineffectually against his broad chest, her fingertips crackling.

"Which part of _'I'm not asking for your permission'_ did you not understand?"

"You don't even realize what you're getting yourself into."

"Of course I –"

"What happens when he inevitably offs some unsuspecting slack that, oh I don't know, bumps into him at the grocery store?" His words hung heavily in the charged air between them, their irony not lost on her. "Or spills coffee on his shoes? Or cuts him off in traffic? How many chances is he going to get before you realize he's a rabid dog that needs to be _put down_ , not molly-coddled."

"Were you even there for the conversation we've been having for the past hour? I. Won't. Let him."

His answering scoff of disbelief made her blood boil, catapulting her mounting frustration out the window and replacing it will full blown rage – and maybe a tiny bit of hurt. She cocked a brow and raised her chin, challenging him.

"You don't think I can?"

Damon's icy stare met hers, her low, clipped tone causing the hairs on the back of his neck to stand at attention. He felt a surge of satisfaction at the anger in her eyes, her normally sage orbs darkening to a deep pine. Taking note of the neon 'CAUTION' sign that was practically flashing above her head, Damon stubbornly chose to ignore it, ducking his head so he was eye-to-eye with the witch.

"That's not it at all Bon-Bon," he goaded, his voice sickly sweet. "I don't think you _will_."

A low hum, like the one powerlines make if you listen closely, was Damon's only warning before he was blasted off his feet, flying back until he crashed into a large bookshelf, crumpling to the ground in an undignified heap, books and various shelving ornaments raining down around him.

He groaned loudly, feeling the familiar crunch of broken ribs and looked up in time to see Bonnie dart from the house, the door slamming shut behind her.

Ignoring the sickening feeling of bone grating against bone, he launched himself forward, intent on grabbing his pig-headed companion and locking her away in the cellar until she regained her sanity, but was stopped in his tracks when he smashed face-first into an invisible barrier at the threshold of his _own damn house._

He growled, seeing red as Bonnie hurried down the driveway toward her car, refusing to even spare him a glance over her shoulder.

Yanking on the driver's side handle, Bonnie squared her jaw as she pulled the door shut behind her, cutting off Damon's angry shout as he pounded a fist against her blockade. Hands shaking with a combination of adrenaline and anger, it took her at least three tries before she succeeded in jamming the key into the ignition, twisting it savagely and stomping down on the gas, sending her squealing away from the Salvatore Mansion.

That absolute _ass_.

Even after everything they'd been through – pre, during and post 1994 – he still had the gall to suggest she couldn't do what it took to keep said 'rabid dog' on a leash. Her teeth ground together as she gripped the steering wheel hard enough to turn her knuckles white, skin tingling with static as her magic raged inside of her, answering her wrath with a jubilant readiness that made her blood sing.

She gripped the wheel tighter.

"That was super fun, but next time would you mind cracking a window? It is pretty steamy in here, and for once it isn't because of me."

Kai was nearly sent straight through the windshield when she slammed on the brakes.

Screeching to a halt, Bonnie swiveled, clutching at her chest to try and prevent her heart from bursting through her ribs, her wide eyes landing on his long figure sprawled across the back seat.

"What the –"

"– hell am I doing in your car? Look at us, already finishing each other's sentences!" He finished as he flashed her a cheeky grin, rubbing the spot on his forehead that had connected with the dash as a result of her extreme driving exercise. "I was just making sure you actually intended to go through with your end of the bargain.

"Kai-"

"And might I say, I'm a fan of the way you negotiate. Or rather, a fan of the way you _don't_."

"Stop-"

"Screw that guy for thinking he can tell you what to do, am I right? Girl-power!"

"Kai-"

"And that bit where you tossed him around like a sack of potatoes? Hi-larious."

 _"KAI!"_

"That's my name, don't wear it out."

The shock of him appearing practically on top of her had been enough to shatter the fragile hold she had on the magic roiling within her. While he had been carrying on with his little monologue, Bonnie had been trying in vain to reign in the surges of energy trying to tear out of her.

Or _through_ her, she wasn't sure which.

Her vision was narrowing, breath coming out in shallow pants as she struggled against the intoxicating current racing over her skin, making her bones practically vibrate with its intensity.

As if on cue, a loud _CRACK_ sliced through the air as a tongue of magic escaped, lapping at the door and spider webbing the windows, causing the steel frame of the car to groan. The sound matched her own as she wrapped her arms around her middle, sweat beading on her forehead.

Kai was beside her in a flash, his bruising grip on her shoulders pushing her back against the seat, all traces of humour wiped from his face.

"Bonnie, you need to calm down."

"I _can't_ …" She bit out.

"Yes you can, just like we practiced," his eyes darted up as the roof dented inward with a _BANG_ , cutting their headroom nearly in half. "Bonnie…"

 _"I'm trying!"_

"Try harder!"

She squeezed her eyes shut in one final attempt to get herself under control, fingernails biting into her palms, worried her teeth were going to shatter with how tightly her jaw was clenched. It hurt, her skin felt like it was being pricked by millions of tiny needles and her muscles ached, tensing as huge swells of unrestrained power battered mercilessly against her failing defences, cresting over them and making her feel as though she was being swallowed whole. Vaguely, she could hear Kai's voice trickling past the roaring in her ears as the feel of his hands on her body faded, an awful numbness washing away his anchoring grip as it ate its way through her limbs. A bolt of fear stiffened her spine.

Magic never used to be like this.

Before getting her powers back in the prison world, she had to focus in order to use them; they didn't just come bubbling up to the surface whenever she pleased. Bonnie had always thought of herself as a kind of channeller; drawing her energy from talismans, celestial events, sacrifices, spells, whatever she needed and molding it to fit her purpose. But this…

Now, it was like the magic came from inside her. She didn't need to pull it from her environment, it was always poised and ready, waiting impatiently at the tips of her fingers to bend to her will. It was thrilling at first, not needing to wait for a full moon to do a spell that would normally have left her too drained to levitate a feather for days afterward. It made her feel strong. But then she started having little accidents; charring someone's hand when they got too close, short circuiting her laptop more than once when she was lost in a daydream, and waking up to find her sheets in flames. Thankfully, neither Caroline nor Elena had been present for that last episode.

And that was the real reason she had struck a deal with Kai. Not because she wanted to fix him, not because she had seen any redeeming qualities in the man since he had merged with his brother – though even she had felt a flicker of gratitude when he had helped Caroline's mom – but because she needed to.

An awful squealing filled her ears, tearing through whatever stupor she fallen into and then suddenly she was outside, her back flat against the road, Kai's weight crushing her against the hot concrete as she got an up-close look at his clavicle. A hoarse gasp rattled through her, her lungs burning urgently as she shoved him away from her, feeling like she hadn't taken a breath in years. Coughing and retching violently, Bonnie felt unwilling tears spring to her eyes as her nerve endings turned to ash. The uncontrollable swell of magic, having apparently burnt itself out, was retreating back from whence it came; tearing its way through her as she writhed helplessly on the pavement. It was like being the Anchor all over again, only a hundred times worse.

And then it was over.

Her eyes snapped open, though she couldn't remember closing them, focusing on the bruised and bloodied man sprawled beside her, his cobalt eyes wide and wary.

They lay there, chests heaving, for five minutes or an hour until Kai cautiously pushed himself up onto his haunches, his gaze catching on something over her shoulder.

"We should probably bump those lessons up to twice a week."

There was a quiet whoosh, followed by loud crackling and a gentle heat behind her. Bonnie used what meagre strength she had left to roll onto her back, her head lolling bonelessly to the side as she watched her crumpled tin-can of a car – or what was left of it – literally go up in smoke.

"Maybe three."


	2. Chapter 2

He watched the little witch struggle, fists balling, chest heaving, jaw clenching, and all he could think was how much more fun it would have been for the both of them if he were using something other than magic to elicit a similar reaction.

Wrenching his mind from the gutter, Kai ended the spell with a flick of his wrist.

Bonnie's eyes snapped open, two bits of jade drilling into him mercilessly, "What are you doing?"

"This isn't working," he sighed, standing to brush the pine needles from his jeans. "I don't think you're trying hard enough."

She scoffed, mirroring his movements, "I'm not _trying_ hard enough? It feels like I just ran a marathon!"

"Bonnie, we've been at this for weeks and nothing has changed. You've had to replace your sheets four times in less than a month, I don't know about you but that's enough evidence for me to confidently say _this isn't working._ " he said flatly, enjoying the way she began spluttering furiously at his honesty. "Also, I'm bored."

"I'm so sorry this isn't more exciting for you," she sneered. "But I don't remember you coming up with any brilliant Gemini-solutions to my little _problem._ And it's not like you're not the one footing my linen bill, so until I can figure out a better way to do this we're sticking to the plan."

"The one where we literally accomplish nothing?" He stifled a chuckle at her vicious expression, splaying his hands in a gesture of mock surrender, "Hey, don't shoot the messenger - I'm just _practicing my honesty_."

"Shut up and do the spell again."

"Bonnie – "

"I said do it again!"

Kai couldn't help the finger of excitement that curled in his belly at her commanding tone, eyes following a bead of moisture as it slid from her temple, down along the column of her throat before disappearing beneath the collar of her T-shirt. The thin material was damp with sweat and clinging to her in ways that was making it increasingly difficult for him to concentrate.

"Okay, _you_ need to cool it before you light something on fire," he watched her deflate slightly at his firm tone, or maybe she was legitimately worried about charring a tree. "Take a minute, drink some water – I've heard people who run _actual_ marathons sometimes upend a bottle on themselves, so maybe give that a try… _Ow!"_

He scowled at her, fighting back a grin at her haughty expression as he rubbed his arms, banishing the stinging hex she had caught him with, "Really?"

She shrugged carelessly, breezing by him on the way to her car; reversing the damage she had done to it had been a fun little project for Kai, kind of like a magical Rubik's cube, only burnt to a crisp and soaked in gasoline. He noticed the sky above them had begun adopting a pinkish hue, and was genuinely shocked to see how much time had elapsed since he had last consulted the watch on his wrist.

"We should probably get going," he called over his shoulder. "It'll be dark soon."

A dull crunch announced the arrival of his own bottle, tossed unceremoniously by Bonnie to land at his feet.

"Again."

He released a heavy sigh, the determined look on her face telling him he had already lost the argument before saying a word. Bending down, he scooped up the bottle and drained half in several long pulls, resealing and tossing it aside with a flourish. He rubbed his palms together, ready to try something a little different. Eyeing her critically, he mumbled a quick incantation under his breath that made the air around her shimmer like a mirage.

The Gemini coven had at their expense a vast arsenal of peculiar little spells that many would take one look at and disregard, such as the one he just used. What advantage could one gain from being able to visualize another witch's magical aura? Not a huge one, unless they were trying to hide it.

And Bonnie Bennet _certainly_ wasn't shy.

Kai ignored her for a moment, a challenge in and of itself, examining the colours roiling around her body like a tide that couldn't decide if it was coming or going. His initial thought was that it seemed large, too large for someone as young as she, but maybe that was just a Bennet thing? He had once caught a glimpse of her grandmother's before she had helped his father lock him up and throw away the key, and remembered it had dwarfed even the great Joshua Parker's. Hers was mostly green as Sheila's had been, a light mossy shade with a few flecks of gold and a darker green sewn throughout. His eyes snagged momentarily on a dusky wisp, but then the lengthening shadows shifted, erasing it and his alarm in one fell swoop.

"Well? What are you waiting for?"

Her flagrant impatience sent a surge of anticipation through him as his own magic coiled readily in response, eager to be unbridled.

Bonnie's only warning was the subtle darkening of Kai's gaze, and then suddenly she was staring up at the blackening sky, a jagged root poking into her back. Sucking in a pained breath, she struggled to her feet, anger heating her already slick skin, "What the hell – "

Another magical blow, this one sending her tumbling into the trunk of a nearby tree. She grit her teeth against the feel of bark scraping against her shoulder, "Kai…"

He ignored her, sending another pulse of energy her way, this one flattening her against the forest floor and crushing the air from her lungs. Clenching her jaw against the swell of magic demanding to be unleashed, she relieved an ounce of the pressure by sending him flying away from her, his back connecting with a tree with an unpleasant _SMACK._

Bonnie scrambled to her feet, her skin on fire.

"Kai, _stop_."

His only answer was a predatory grin that sent her heart into overdrive, a twinge of fear whipping her magic into an even finer frenzy. Pushing himself off the tree, his back throbbing, Kai analyzed the tempest of colour before him. Oddly enough, his first thought was that it was actually kind of… beautiful? But in a humbling way, like watching a tornado touch down or seeing a massive ocean swell cresting just before it crashed into the beach; beautiful and powerful and _dangerous_. As he watched her try to reign in the writhing emerald mass, he could feel the air around them shifting, charging with static, making the hairs on the back of his neck stand on end. He shot another spell her way, fascinated by the explosion of movement and colour it caused as Bonnie staggering back; it reminded him of dropping a stone into a pond, if the stone weighed a ton and the pond was filled with hydrochloric acid.

She looked like she was caught in the middle of a fireworks display gone wrong.

Distracted by the spectacle, he didn't notice her spell until it hit him square in the chest, making him feel like he was that rock at the bottom of the pond, dissolving from the inside out. Growling out the counter-curse between clenched teeth, his next spell drew a moan of pain from the witch as she clutched her head in agony. Her aura was pulsing, stretching outward to fill any available space. He noticed his own magic reacting to the pull of hers, pausing his magical onslaught to study the curious feeling.

Having round-the-clock powers was a feeling that still needed a little getting used to for Kai. Despite having merged with Luke more than a month ago, he sometimes still forgot he now had the ability to practice magic whenever he pleased. Gone were the days when he was forced to rely on others to produce even the simplest of spells and boy was he glad of that, but he was still learning how to exist in this new, exceptionally more convenient world. Despite not being born with powers of his own, Kai had always been proficient in the art of all things magical. When he was young, he had outperformed his twin and other witches his age and older at every opportunity; learning quickly became a matter of survival when his practice time was limited to whenever he could draw magic from another witch. The transition from being a Siphon to having the power of the entire Gemini coven at his fingertips was still ongoing, and _this_ was an entirely new experience.

It felt like Bonnie was a magnet and every molecule of his being was coated in iron. He imagined if he could see his own aura it would be reaching for hers, stems of power stretching and straining to meet her own. He felt tense, coiled tight like a spring as he watched her shake off his spell, excitement rolling over him in a searing wave when her eyes found his, magic flaring blindingly around her.

Kai resisted the urge to move towards her, the imagery of what occurs if a moth flies too close to a flame helping to stay his eager feet. He deflected the next round of spells she aimed at him, failing to conceal his smile as she grew more and more frustrated with every failed attempt to boil him alive. He couldn't help it, he'd never felt so… _alive._ His heart was pounding, his skin was slick with sweat, and every time Bonnie sent a burst of magic his way, his own roared with barely restrained glee, rushing forward to crash against hers with a sound like a thunderclap.

He wondered vaguely if anyone was hiking nearby, thinking they were likely to believe there was an electrical storm rolling in if they were inside five miles.

Suddenly he was being hurled across the clearing, landing hard on a particularly rocky patch of ground. The wind knocked out of him, Kai gasped soundlessly for breath and felt himself being dragged by an unseen force. Lifting his head, his eyes landed on Bonnie, her lips moving through a mumbled incantation as she curled one delicate finger over and over, summoning him closer. His magic tensed hungrily, preparing to pounce and the closer he got, the more he felt his control slipping. It was like she was _pulling_ the power out of him.

Was this what being siphoned felt like?

The distance between them had already halved by the time Kai thought to dig his heels into the earth to slow his progress.

He could have sworn he saw a smile kink her lips.

Her aura was lapping at his feet now, pine and sage and olive and mint all swirling together in a dizzying current that felt like fire and ice against his skin; it was addictive. Pins and needles crawled up the length of his body as he was pulled toward her, cauterizing his shins, his thighs, his groin…

"Bonnie – "

The jagged sound did nothing to halt his progress, if anything his voice only added fuel to the fire burning in her eyes. A flicker of anticipation shot through him – what was she going to do once she had him in front of her?

Kai was less than a dozen feet from her when he finally managed to interrupt the spell, breaking her hold and sending her stumbling back a few steps, which was slightly concerning as he had been aiming to launch her into the next _state_.

She began moving toward him, her movements unhurried, the smile on her lips anything but friendly. The look on her face sent a pang of something unfamiliar but not entirely unpleasant through his gut.

The pins and needles resumed, crawling over his abdomen and up his chest, making it hard to breathe. He was paralyzed watching her close in on her prey; exuding pure, raw power in waves that left him feeling like his entire body was one big, exposed nerve. His magic howled and beat against him, trying to escape his grip so it could tear her apart.

Or was it him that wanted to tear her apart?

All he could see was green.

Self-preservation taking over, Kai twisted his wrist savagely and sent Bonnie hurtling straight up through the canopy, his breath returning to him in harsh gasps as the distance between them increased. Mumbling a quick _invisique_ , he scrambled to his feet and released the magical hold, prepared to cushion her fall if necessary. He barely noticed as the wind picked up, sending leaves and pine needles skittering around his feet. When Bonnie reappeared, descending smoothly through the branches and clearly _not_ needing his help, Kai went the extra step and masked his own aura to ensure she wouldn't be able to sense him.

Bonnie touched down unsteadily in the centre of the clearing. Stumbling forward a few steps, she hunched over, pressing her hands against her knees and breathed deeply in an attempt to stanch the flow of magic rushing through her. Sparing a glance around the clearing to find no sign of the Gemini leader made matters worse, nervousness gripping her and upsetting her focus enough for a wave of magic to escape, hissing and crackling so loudly it made her ears pop.

Bonnie growled impatiently, clamping down hard and feeling her powers squirm and writhe violently in protest. Hair whipping around her face, she welcomed the chill that came over her as a harsh wind kissed her damp skin, soothing the sting of her magic. It was still fighting her, trying fiercely to shake off the leash she had slipped around its neck.

She was so goddamn _tired_ of this.

Dropping to her knees on the forest floor, she bared her teeth in a snarl and dug her fingers into the cool, damp dirt, wrenching back against the feral creature with every ounce of her strength until finally, the torrent shifted. It was like someone had flipped the 'off' switch, restricting the flow of power bit by bit until nothing but a trickle remained.

Bonnie released a breath she hadn't realized she was holding, the sound seeming thunderous in the quite of the clearing. Too quiet, she realized with a start.

Raising her head, she barely managed to contain a scream when she noticed Kai standing directly in front of her stooped form. Scrambling to her feet, she stumbled back a few steps and nearly tripped over a raised root as he reached out a hand to steady her.

A blinding spark illuminated the shadowy clearing the instant Kai touched her, a loud _CRACK_ echoing through the trees as he jerked his hand back as though he'd been burned.

Quickly fading to quiet, the only sound that remained was their harsh pants. The two witches regarded one another cautiously as the last sliver of sun finally dipped below the horizon, leaving the sky to burn in its wake.


End file.
